To facilitate consumer access to household products, it is often attempted to provide packaging with easy opening features. In the case of soap bar cartons, for instance, previous efforts have included provision for weakening a portion of an underlying closure flap which is glued to an overlying flap. The underlying flap portion is weakened to such an extent that when the overlying flap is lifted the weakened portion of the underlying flap is torn from the underlying flap, thereby opening the carton. Specifically, a window may be created in the upper surface of the underlying flap which comprises cut scorelines generally parallel to, but recessed from, the rectangular boundaries of the flap, which window is glued to the overlying flap and delaminates when the overlying flap is pulled.
Patents disclosing weakened portions defined by scores or cuts include Brown U.S. Pat. No. 2,828,060, Tyrseck U.S. Pat. No. 3,015,432, Brastad U.S. Pat. Nos. 3,491,937 and 3,719,317 and Kienlen U.S. Pat. No. 2,259,822.
A problem attendant to the use of the previous window delaminating flaps is that there is a tendency for any cut scorelines parallel to the fold line separating the flap from the main panel to become fold lines in the processing of the package. The folding of the flap along cut scorelines can readily cause problems in the sealing of the package as where the cut scoreline folds in a direction lengthwise of the flap. Such lengthwise folding of the flap may make it difficult to adhere effectively the outer flap to the underlying flap.
Various types of cartons are disclosed in the prior art, including those illustrated in U.S. Pat. Nos. 2,852,180; 2,881,968; 2,884,180; 2,936,104 and 2,992,767.
Meyers U.S. Pat. No. 4,124,161 discloses that when sealing gases are applied to the top of the underlying flaps the flaps tend to droop, which interferes with sealing. Meyers makes a cut score along substantially the entire length of the top of the underlying flaps indented from the fold lines of the flap to provide sealing margins. The cut scores may be in the form of a straight line or in sine wave or other non-linear shapes shown in Meyers' FIG. 5. The non-linear scorelines are said to be stronger than the straight cut scorelines.
Redpath et al. U.S. Pat. No. 3,295,743 discloses a carton having a zigzag cut scoreline 31 extending across the front panel. Spots of adhesive are located between the zigzag cut scoreline 31 and the upper edge of the front wall when the carton is glued in tubular form. The arrangement is said to permit the outer surface of the panel to peel off readily when the carton is opened if the adhesive is bonded sufficiently not to come loose when the carton is opened.
Green U.S. Pat. No. 3,113,713 discloses glue applied in a special pattern of decreasing bonding area in the direction of pull allowing the ease of opening to be increased and the opening speed to be accelerated as pull is exerted. Triangular areas are illustrated.